You can use an Uno to program an ATTiny85 ($1) and have 5 pins (2PWM*) for I/O, or an ATTiny84 ($2) for a few more. If you have any intention of doing this with more models in the future this is the route you should take to save money.
- You can use software PWM or a supporting chip like the TLC5940 for more pins but that's a more advanced topic.